1. Field of the Invention
The present invention relates to an image sensor module for use in e.g. a document scanner. The invention also relates to an LED module used for such an image sensor module.
2. Description of the Related Art
FIG. 13 shows an example of a conventional image sensor module. The image sensor module 900 shown in the figure is designed to read the content of a read object 890 transferred in a secondary scanning direction y as image data. The image sensor module 900 includes a case 91, a substrate 92, an LED module 93, a light guide 94, a lens unit 95, a sensor IC 96, and a light-transmitting plate 97. The case 91 is elongated in the primary scanning direction perpendicular to the secondary scanning direction y and the thickness direction z. The substrate 92 is in the form of a rectangle elongated in the primary scanning direction and fitted in the case 91. The LED module 93 includes a plurality of LED chips 93a and arranged at one of the ends of the case 91 which are spaced from each other in the primary scanning direction.
The light guide 94 guides the light emitted from the LED module 93 toward the read object 890 and is made of transparent resin. The light guide 94 is elongated in the primary scanning direction and includes an incident surface (not shown), a reflective surface 94a, and an emission surface 94b. The incident surface is one of the end surfaces of the light guide 94 which are spaced from each other in the primary scanning direction and faces the LED chips 93a. The reflective surface 94a reflects the light traveling from the incident surface. The emission surface 94b is elongated in the primary scanning direction and allows the light traveling through the light guide 94 to be emitted toward the read object 890 as linear light elongated in the primary scanning direction. The light emitted from the light guide 94 becomes incident on the read object 890 through the light-transmitting plate 97 and is reflected by the read object 890. The reflected light is converged onto the sensor IC 96 by the lens unit 95. The sensor IC 96 is configured to output a signal corresponding to the amount of light received. The signals outputted from the sensor IC 96 is stored in a memory (not shown), whereby the content of the read object 890 is read as an image.
To realize size reduction of the image sensor module 900, size reduction of the LED module 93 is necessary. The size of the LED module 93 largely depends on the arrangement of the LED chips 93a. For the LED chips 93a, bonding onto leads (not shown) or connection using a wire is essential. Dense arrangement of the LED chips 93a makes it difficult to arrange bonding layers or wires for the bonding.
When the read object 890 has a fold or a wrinkle, the read object 890 tends to separate from the surface of the light-transmitting plate 97. In such a case, to clearly form an image of the content of the read object 890 onto the sensor IC 96, it is desirable to make the light path extending from the read object 890 to the sensor IC 96 longer. However, when the sensor IC 96 is arranged at a lower position to make the light path longer, the dimension of the image sensor module 900 in the thickness direction z increases, making it difficult to incorporate the image sensor module 900 in e.g. a document scanner.
FIG. 37 shows an example of conventional document scanner (see Patent Document 2, for example.) The document scanner 900 shown in the figure includes image sensor modules 910, 920, a pair of driving rollers 930, a pair of driven rollers 940, and a case 950. The paired driving rollers 930 are spaced apart from each other, with the image sensor module 910 intervening between them. The paired driven rollers 940 are spaced apart from each other, with the image sensor module 920 intervening between them. The read object 890 is transferred between the image sensor modules 910 and 920 while being sandwiched between the driving rollers 930 and the driven rollers 940. In this process, the content described on the lower surface of the read object 890 is read by the image sensor module 910, while the content described on the upper surface of read object 890 is read by the image sensor module 920.
In recent years, there is an increasing demand for size reduction of document scanners. For instance, reduction in dimension of the document scanner 900 in the transfer direction of read object 890 is desired. Further, reduction in dimension in the thickness direction of the read object 890 is also demanded. With the conventional arrangement, however, to avoid contact of the image sensor modules 910, 920 with the driving or driven rollers 930, 940, there is a limit on reduction in dimension of the document scanner 900 in the transfer direction of the read object 890. Further, to make the document scanner 900 thinner, the image sensor modules 910, 920 need to be made thinner.    Patent Document 1: JP-A-2007-300536    Patent Document 2: JP-A-2008-285259